Electroplating apparatus



July 27, '1943. G. J. HURLsToN 2,325,401

ELECTROPLATING APPARATUS Filed OG'C. l?, 1940 @E A? .E J /L/ @570m @ZM/f @am fifa/Wa?.

Patented July 27, 1943 ELEoTnoPLA'rING APPARATUS George J. Hurlston,

Carnegie-Illinois tion of New Jersey Pittsburgh, Pa., assignor to Steel Corporation, a.

Application October 17, 1940, Serial No. 361,641

4 Claims.

This invention is primarily concerned with apparatus for electroplating metal strip. wire and similar work passed continuously through an electrolyte at varying traveling speed. However, the principles of the invention may be considered applicable to other electrolytic treatment of such work.

The accompanying drawing schematically illustrates an example of apparatus the principles of the invention.

In this drawing, vthe work W is shown as being passed continuously through an electrolyte in a tank T, this being done by means of guide rollers R.. It is to be understood that although the value of the traveling speed of this work may be a constant a great deal of the time, this value varies one or more times during the passage of the work through the electrolyte. For instance, assuming thework to be strip steel and the tank T and rollers R to represent part of a group f equipment for electroplating this strip, it may be necessary embodying to slow down the normal traveling speed of thel strip when it becomes time to fasten its trailing end to the leading end of another length of strip whereby to thread the latter through the equipment, the speed then being returned to normal.

The armature I of a driven generator establishes an electric current between the electrolyte in the tank T and the work W through a circuit 2 which includes a work contactor roller CR and electrodes E immersed in the electrolyte in the tank T above and below the work passing through this electrolyte. If the Work is being electroplated, these electrodes may comprise the plating metal. The output of the armature'l is directly proportional to the strength of the generators field 3 which is powered through a circuit 4 by an exciting generator 5, this circuit 4 containing a rheostat 6 for controlling the strength of the eld 3.

It is obvious that the electroplating or other electrolytic eiect produced on the Work W vwill be of a constant value as long as the traveling speed of the work and the output of the armature I have constant values, assuming that those factors affecting the eiiiciency of the electrolytic effect remain constant. Thus, the temperature and composition of the electrolyte aiect the eiliciency of the electrolytic eiect, but these factors can be held to constant values. Other less controllable factors aecting the eiiiciency of the electrolytc effect` will be discussed later.

When the value of the traveling speed of the Work W varies, it is obvious that the electrolytic eiect of the current on the work must also vary,

and such variation willalso occur if the value of the current established between the work and the electrodes should vary for any reason. The primary function of the present invention is to prevent variations in these values from affectingthe electrolytic eiect produced on the Work by the current between the work and the electrodes, the invention serving to hold this effect constant at all times.

Keeping the above in mind, the circuit 2 includes a shunt 1., and a shunt circuit 8 is in shunt connection with this shunt 1. This circuit 8 also includes the portion of a slide wire 9 selected by a contactor I0 working onvthis slide Wire. The slide Wire 9 is connected 'to a Vsmall generator II by a circuit I2, this generator having a xed eld'strength so that its voltage is directly proportional to its speed and being driven through a Work contacting roller I3 by the traveling work-W so that the Voltage applied the circuit I2 and the slide Wire 9 is directly proportional to the value of the traveling speed of the work W.

The circuit I2 connects the generator II with the slide wire 9 respecting the connection of the shunt circuit 8 with the contactor I 0 and the portion of the slide wire 9 selected thereby, so that the voltage applied the circuit 8 by the drop in the shunt 'I opposes that applied this circuit by the drop in the portion of the slide wire 9 included in the circuit 8 by the contactor I0. When the two voltages are equal no current flows in the circuit 8 but when they are unbalanced current flows in the circuit in one direction or another depending on which source is of the higher voltage.

The operating coil of a contact-making galvanometer I 4 is included in the circuit 8, the contacts of this galvanometer I4 controlling the reversing circuit I5 of a small reversing motor I6 which works the controlling element of the rheostat 6. When the voltage taken from the shunt I is higher than that taken from the slide wire 9 by the contactor I D, the galvanometer I4 causes the motor I6 to operate in a direction moving the controller of the rheostat 6 so as to reduce the strength of the eld 3, whereupon the output of the armature I drops until the voltage taken from the shunt I balances that taken from the silde wire 9 by the contactor I0. When the voltage taken from the shunt I is less than that taken from the slide wire 9 by the contactor I0, the function is opposite, the strength of the field 3 being increased until the output of the armature l increases so that thel voltage taken from the shunt I balances that taken from the slide wire 9 by the contactor I0.

Since the voltage taken from the shunt I is directly proportional to the value of the current between the electrolyte and the work, and since the voltage selected from the slide wire 9 by the contactor Ill is directly proportional to the value of the traveling speed of the work, the apparatus as so far described provides for the continuous maintenance of a ratio between these values that is a constant value. This ratio is not only maintained'constant when the traveling speed value varies, .but is also maintained constant should the electrolyzing current value vary for any reason, the shunt Tbeing in the same circuit with the electrodes E and the Work W whereby should the electrolyzing current drop, the voltage applied the circuit lII from the shunt 'I also drops, whereupon the apparatus reestablishes the ratio.

Another important feature is that this ratio between the current and speed values can beA given any value desired by moving the contactor I over the slide wire 9 so as to vary the ratio between the voltage produced by the generator II and that applied the circuit 8 from this generator by way of the slide wire 9 and contactor I9. For instance, in the case of electroplating, it may be desired to increase the weight of plate applied the Work, and this may be done simply by adjusting the contactor I0 so that the ratio between the voltage produced by the generator II and that applied the circuit 8 from this generator by way of the slide wire 9 and its contactor Ill` is increased, this in eiect increases the ratio of platingy current to traveling speed at which the apparatus operates. Conversely, the weight of the plate may be decreased by adjusting the contactor I0 to decrease the current to traveling speed ratio. Once the ratio has been selected, the apparatus maintains its value constant, the rheostat 6 being practically immediately adjusted upon any changes in the value of this ratio so as to establish the value selected.

It was previously'mentioned that the temperature and composition of the bath may be kept at constant values. However, the eiciency of the eelctrolytic effect on the work may also vary in accordance with the electrolyzing current and the travelling speed values. That is to say, when the traveling speed value varies the electrolytic eiect produced-on the work may not be the same even though the ratio of electrolyzing current to traveling speed is maintained at a constant value by the apparatus previously described. In some instances, the ratio between the current and the traveling speed values must be increased as the traveling speed value increases, while in otherv instances the ratio must be decreased. In addition, it is sometimes necessary to increase the ratio as the current value increases, or to decrease this ratio when the current value decreases. All this obviously presents complications.

Returning to the drawing, in addition to the slide wire 9 the circuit I2 may be made to include the resistances I8 and I9 of two rheostats. The controlling elements and 2i of the latter are connected into the circuit I2 by ythe switches 20a and 20h, and 42Ia and 2|", respectively. The resistances I8 and I9 are ineffective when all four switches are closed, as shown in the drawing.

The element 20 is mechanically connected with the motor IB, making it move with the element oi the rheostat 6 so that when the switches 2I and 2lb are closed to make the resistance I9 ineffective and either switch 20B or 20h is opened, more or less of the resistance I8 will be placed in the circuit I2 and so in series with the slide wire 9, the amount of this resistance depending on the operation of the motor I6. When the switch 20a is closed and the switch 2l)b opened, more of the resistance I8 is placed in series with the slide wire 9 as the motor I6 moves the element of the rheostat 6 so as to reduce the eld strength 3. It follows that as the output of the armature I decreases, the voltage taken from the slide wire 9 by the contactor I0 automatically decreases, whereby the ratio between the electrolyzing current value and the traveling speed value decreases as the electrolyzlng current decreases. The opposite effect is secured when the switch 2mJ is closed and the switch 2liaL is opened, and when both switches are closed, the resistance I8 has no effect on the voltage in the slide wire 9. The apparatus then maintains the ratio between the current and the traveling speed values at a constant value as previously described.

The controller 2l of the resistance I9 is operated by a reversing motor I6, a fixed resistance 22 .being placed across the circuit I2. The voltage drop across the resistance 22 is directly proportional to the output of the generator II and, therefore, to the traveling speed of the work W. The motor ItEL is controlled in substantially the same manner as described in connection with the motor I8. For this reason the various parts involved are numbered the same as those involved in the control of the motor I6 and are identified by the letter a, the only diierence being that the slide wire 9a is energized by a battery IIa controlled by a variable resistance I3, and the contactor Illa being driven by the motor 56a so that the voltage taken from slide wire 9B by the contactor llia is maintained equal to that across the resistance 22.

With the above arrangement, when the value of the voltage in the circuit I2 varies by reason of the traveling speed value varying, current ows in the circuit 8a in one direction or another depending on whether the voltage taken from the slide wire 9a is greater or less than that taken from the resistance 22. Therefore, assuming the Switches ZIJa and 2Gb to be closed, it is possible to vary the voltage in the slide wire 9 so as to result in the value of the ratio between the current and the traveling speed values either increasing or decreasing as the traveling speed value varies. The eiect secured depends on the operation of the switches 2 I a and 2 Ib.

When both resistances I8 and I9 are made effective the ratio of electrolyzing current to traveling speed is automatically changed to compensate changes in efciency of the electrolytic effect on the work resulting from changes in either or both electrolyzing current and traveling speed.

It is to be understood that the rheostats including the resistances I8 and I9 must be calibrated to operate in accordance with the characteristics of the electrolyte being used and the electrolytic action involved. In some instances these factors are known, but, in any event, they can be experimentally determined.

The present invention ris a continuation, in part, of the invention disclosed in a copending application filed by the same inventor on February 23, 1937, and bearing Serial No 127,276.

I claim: l

l. Apparatus for electrolytically treating metal strip and wire work, including the combination of an electrolyte, equipment for passing said work continuously through said electrolyte at a varying traveling speed, a first electric circuit including said work and said electrolyte, electric powering means for said iirst circuit, a second electric circuit, means for obtaining an electric voltage in said second circuit proportional to the current in said iirst circuit, means for obtaining an electric voltage in said second circuit proportional to said traveling speed in opposition to the voltage obtained by the second named means and means responsive to the direction of the current flow in said second circuit for varying the output of said powering means, said combination further including adjustable means for varying the voltage obtained in said second circuit by at least one of said means for obtaining an electric voltage therein.-

2. Apparatus for electrolytically treating metal strip and wire work, including the combination of an electrolyte, equipment for passing said Work continuously through said electrolyte at a varying traveling speed, a first electric circuit including said work and said electrolyte, electric powering means for said iirst circuit, a second electric circuit, means for obtaining an electric voltage in said second circuit proportional to the current in said first circuit, means for obtaining an electric voltage in said second circuit proportional to said traveling speed in opposition to the voltage obtained by the second named means, and means responsive to the direction of the current ow in said second circuit for Varying the output of said powering means.

3. Apparatus for electrolytically treating metal strip and wire work, including-the combination of an electrolyte, eequipment for passing said work continuously through said electrolyte at a varying traveling speed, a rst electric circuit including said work and said electrolyte, electric powering means for said first circuit, a second electric circuit, means for obtaining an electric voltage in said second circuit proportional to the current in said first circuit, means for obtaining an electric voltage in said second circuit proportional to said traveling speed in opposition to the voltage obtained by the second named means, and means responsive to the direction of the current iiow in said second circuit for varying the output of said powering means, said second circuit including means responsive to operation of the fourth named means for varying the current flow in said second circuit.

4. Apparatus for electrolytically treating metal strip and wire work, including the combination of an electrolyte equipment for passing said work continuously through said electrolyte at a varying traveling speed, a first electric circuit including said work and said electrolyte, electric powering means for said irst circuit, a second electric circuit, means for obtaining an electric voltage in said second circuit proportional to the current in said first circuit, means for obtaining an electric voltage in said second circuit proportional to said traveling speed in opposition to the voltage obtained by the second named means, and means responsive to the direction of the current flow in said second circuit for Varying the output of said powering means, said second circuit including means responsive to said traveling speed for varying the current iiow in said second circuit.

GEORGE J. HURLSTON. 

